1. Field of the Invention
The present invention relates to a method, in an image processing means comprising a number of (n) processor modules, of processing data from a document, in which image data originating from a number of predetermined zones of the document are fed to a processor module and processed per zone. The invention also relates to an image processing apparatus comprising a number of (n) processor modules, each connected to a bit-map memory, for processing data obtained by linewise photoelectric scanning of a document, in which data from a number of predetermined zones of the document are fed to a processor module, stored in part of the bit-map memory and processed per zone.
A method and apparatus of this kind are used for processing data originating from an electronic desktop publishing system or originating from a scanner, in which a document is electrically scanned by means of a CCD-array. The resulting data are processed in an image processing means and then fed to a printing system, e.g. an LED or laser printer. To obtain rapid image processing, the scan signals (or data) are fed to a number of parallel-connected processor modules each provided with a local bit-map memory in which the data are stored, and which can then perform a number of operations on such data, e.g. dithering, fourier transformation, rotation and so on. After these operations, the processed data stored in the bit-map memories are read out and fed to a printer.
2. Description of Related Art
The local bit-map memories of known processors are so arranged that each offers space for data originating from a vertical strip of a document. A number of parallel-connected processor modules are thus able to process an entire document in parallel. An example of this is described in Netherlands Patent Application No. 8801116, which corresponds to U.S. application Ser. No. 07/342,988 filed Apr. 24, 1989.
A method of image processing as known from the prior art will now be described with reference to FIG. 1. A number of (4) processor modules 15-18 are connected to a distribution means 19. A document 26 is fed in the direction of arrow 27 past a CCD array 20. The analog signals obtained are converted via an A/D converter 28 into digital image data and fed via bus 21 to the distribution means 19. The latter distributes the image data in such a manner that data from zone 22 of the document is fed to processor module 15 and stored in local bit-map memory 29. Similarly, data from zone 23 are fed to module 16 and stored in local bit-map memory 30, data from zones 24 and 25, respectively, are fed to modules 17 and 18 and stored in respective local bit-map memories 31 and 32.
The processor module 15 processes the data from local bit-map memory 29 and at the same time the other processor modules perform the same process on data from their local bit-map memories. The processed data are then returned to the local bit-map memories.
For some processing operations, data from other local bit-map memories must also be fed to a specific processor module. This mutual exchange is carried out via a communication channel 33.
The processed data in the local bit-map memories 29-32 are then fed to a printer (not shown) via the processor modules 15-18 and via a second distribution means (not shown).
Since each processor module processes data from a fixed vertical strip of the document, the parallel-connected processor modules are not all subjected to equal loading in the case of data-sensitive operations, such as skeleton generation. A processor module which processes data from the edges of a document, in which there is usually little information (low data density), will carry out its task more quickly than a processor module which processes data from a central strip of the document which has a higher data density. The result of this uneven loading of the processor modules is that the processing time of a document is not optimized.
The process described above with respect to FIG. 1 therefore realizes the following disadvantage. The processor modules 15 and 18 required to process the data from the marginal zones 22 and 25 of the document 26 will frequently have performed these processing operations much faster than the processor modules 16 and 17, so that this disproportionate loading results in a relatively long processing time for the data of the entire document 26.